A variety of substantially water insoluble particulates are known and useful in treating fabrics. For example, particulate pigments, such as ultramarine blue, are used to mask the undesirable yellow color of fabrics following laundering. During laundering, if the pigment particles are sufficiently small and are dispersed in the laundry solution, then they become entrained in the fabrics. Thus, for example, ultramarine blue particles can be used to mask the yellowed color of the fabrics by partially compensating for the absorption of short wavelength blue.
Although addition of particulates in conjunction with laundering additives is a convenient means of treating fabrics, it has been difficult to sufficiently stably suspend the particulates, particularly in a strongly oxidizing environment such as hypochlorite bleach, while retaining water dispersibility of the solution.
U.S. Pat. No. 4,271,030, issued June 2, 1981, inventors Brierley et al., discloses a liquid hypochlorite bleach having a particulate pigment, such as ultramarine blue, which is said to be stably suspended in the composition by means of a flocculant, such as calcium soap flocs and amine oxides, filling at least 50% of the volume of the composition; and, U.S. Pat. No. 3,663,442, issued May 16, 1972, inventor Briggs, discloses liquid bleaching compositions having a finely particulate styrene copolymer which imparts opacity to the compositions. The styrene copolymer is emulsion polymerized by means of an emulsifying surfactant.
U.S. Pat. No. 3,393,153 to Zimmerer et al., issued July 16, 1968, discloses the use of an oxidized polyethylene emulsion as a stabilizing agent for dispersions of fluorescent whitening agents in bleach. Formation of these emulsions, however, requires the use of surfactant, and the resultant emulsions have been shown substantially to lack both physical and chemical stability.
U.S. Pat. No. 4,526,700, inventors Hensley et al., issued July 2, 1985, discloses aqueous hypochlorite bleach compositions in which a particular optical brightener is in the form of fibrous particles having a density close to that of the aqueous phase. These fibrous particles are formed by dissolving the brightener and certain alkylaryl sulfonate surfactants in water and adding sodium hypochlorite.
U.S. Pat. Nos. 4,146,499 and 4,472,291, inventor Rosano, issued Mar. 27, 1979 and Sept. 18, 1984, respectively, disclose microemulsions including oil, water, at least a primary surfactant, and an oxidizing agent. The individual polymer droplets are said to be substantially entirely covered by adsorbed surfactant.
Thus, prior liquid bleaching compositions which have had particulate laundry additives dispersed by means of a polymeric material have required the presence of one or more surfactants in order to prevent agglomeration and/or settling of the particulate laundry additives.
Although some surfactants are relatively stable to the strong oxidizing environment of hypochlorite, over time there is a tendency towards degradation of surfactant and this may lead to formation of undesirable by-products in liquid bleaching compositions which include surfactants. Accordingly, it would be desirable to provide liquid bleaching compositions which include stably suspended particulates (such as pigments) and/or fluorescent whitening agents (typically present in crystalline form) without the necessity of a surfactant as a suspending or co-suspending agent.